The long-term objective of this research program is to define the role of thyrotropin-releasing hormone (TRH) in the pathophysiology of epilepsy. We propose the hypothesis that under certain conditions TRH may function as an endogenous anticonvulsant in specific pathways and loci of the CNS. We will use two seizure paradigms, electroconvulsive shock (ECS) and electrical kindling, along with the following key methods and specific aims to test this hypothesis: 1) A highly specific TRH radioimmunoasay (RIA) to quantitate TRH in subregions of the CNS, and immunocytochemical techniques for TRH and proTRH localization to determine the specific CNS loci and pathways associated with the seizure induced TRH increase; 2) Synthetic oligonucleotides and cDNA technologies for in vitro and in situ hybridization studies will be used to identify and quantitate preproTRH gene expression in those regions of the brain which show increased TRH levels following seizures; 3) Microdialysis in vivo and superfusion in vitro will be used to determine if and where TRH is released acutely and/or chronically following seizures; 4) Microinjections of TRH and/or its analogues will be used to determine if and where in the CNS these compounds are capable of inhibiting the kindling process; and 5) A sensitive in vitro TRH degradation assay will be used to determine whether seizures alter the pattern of TRH breakdown in specific regions of the brain known to contain epileptic foci. The objectives and procedures proposed should yield data which may result in: 1) further understanding the pathogenesis of epilepsy; 2) a theraputic regimen which includes TRH in combination with more conventional anticonvulsant drugs and 3) use of TRH and/or its analogues to block the formation of epileptic foci.